Fritz hasselmann



FRITZ HASSELMANN, OF MUNICH-NYMPIIENBURG, GERMANY.

METHOD OF iMPREGN ATING WOOD.

SPECIFICATION forming part of Letters Patent No. 626,538, dated June 6,1899.

Application filed December 12, 1898. 8erial No. 699,021. (No specimens.)

fibrous substances is described, said process being based upon thetreatment of the wood first with solutions of sulfate of alumina andsulfate of iron oxyhydrate and afterward in a similar manner withsolutions of calcium chloride and caustic lime. This process thusconsists of two consecutive boilings, which have the effect of renderingthe wood so treated firmer and more resistant to and free from theattacks of fungus and rot. At the same time, however, the natural colorof the wood is more or less changed, which for some purposes-as, forinstance, joinery-is desirable for the attainment of certain coloreffects,

but in general is prejudicial to the use of the wood. Anotherinconvenience of this otherwise successful process is the somewhatawkward and expensive double boiling. By the improved process formingthe subject-matter of this invention, however, the wood prepared retainsits natural color, and the second boiling is dispensed with withoutsacrificing any of the advantages of the process of the patent referredto.

My invention consists in the process herein described of impregnatingwood and other vegetable fibrous substances, according to which they areboiled under pressure with a solution of double vitriol, aluminumsulfate, and kainit for several hours.

The process is carried out as follows: The wood is subjected in asuitable apparatus to the action of an aqueous solution of acrystallized mixture of ferric sulfate with from five per cent. tofifteen per cent. of cupric sulfate and aluminum sulfate. As soon as aheat of 105 centigrade is obtained an aqueous solution of kainit in theproportion of one to forty is added in such quantity as is suitable forthe particular purpose and the nature of the wood. The boilingis thencontinued under a pressure of from two and one-half to three atmospheresand at a heat of 135 to 14:0 centigrade, the period of boiling varyingfrom two to four hours, according to the kind of wood to be treated, forconifer woods the time beinglonger than for others. By this treatment achemical change takes place in the sappy constituents of the wood andboth the cell-walls of the wood and any contents present in them enterinto permanent chemical combination with the impregnating substances. Asthe cavities', scientifically known as lumina, of the wood-cells,however, are not affected by the treatment, the wood, although gainingessentially in firmness, loses none of its elasticity.

The chemistry of the new process is as follows: As in the United Statespatent referred to, so in this case, iron and aluminum salts areprecipitated and, remaining as such, color the wood fiber to a veryslight extent. Moreover, and this is the main point of the process, thepotassium of the kainit combines with the lignine of the wood to form anew andhitherto unknown substance, which imparts to the impregnated wooda horny character. If, for instance, wood or similar substances beboiled with concentrated solutions of chloride of zinc at a temperatureof about 135 centigrade, these substances change to a tough gelatinoustransparent mass, in which the metal, being chemically combined, is nolonger to be detected by the ordinary reagents. This tough gelatinousmass becomes horn-like in water and is indifferent to acids. Thepotassium chloride of the kainit displays the same characteristics aschloride of zinc or chloride of magnesium,and the chemical processeswith weak solutions under high pressure are the same as with strongsolutions without pressure. From this the important and hitherto-unknownfact is ascertained-'5. 6., that a constituent of the wood enters intochemical combination with the potassium chloride of the kainit used forthe impregnation and, moreover, that this chemical combination isinsoluble-i. 6., cannot be lixiviated by water. It may also be remarkedthat the potassium present in the wood and which remains behind aspotash when the wood is burned also combines in a similar manner, sinceit likewise can only be lixiviated to a very slight extent.

The wood treated by the process described above is considerably harderthan wood which has not been treated and is consequently very suitablefor polished work. It is tougher than before impregnation and isinsensible to the eifects of the'atmosphere, of rot, and of fungi. Itretains its natural color and is consequently applicable for allpurposes, even for such as those for which wood treated by,

claim as new and desire to secure by Letters Patent- 1. The processherein described of impregnating wood and other vegetable fibroussubstances, which consists i'nboiling them under pressure with asolution of crystallized mixture of ferric sulfate and cupric sulfate,aluminum sulfate and kainit, for several hours, substantially as setforth;

2. The process herein described of impregnatin g wood and othervegetable fibrous substances, which consists in subjecting them to theaction of a solution of crystallized mixture of ferric sulfate andcupric sulfate, aluminum sulfate and kainit for several hours at atemperature of from 135 to 140 centigrade and at a pressure of from twoto four atmospheres, substantially as set forth.

In witness whereof I have hereunto signed my name, this 28th day ofNovember, 1898, in the presence of two subscribing witnesses.

FRITZ HASSELMANN.

\Vitnesses:

EMIN L. GoLDsoHMIDT, HENRY HASPER.

